The desirability of exercising a patient's lungs, particularly a postoperative patient, has long been recognized. It is essential for the patient to expand the lungs as soon as possible after surgery, and in some other medical situations, so that all of the alveoli of the lungs are inflated.
For this purpose, many devices known as spirometers have been devised. Although these spirometers take various forms, those which are particularly valuable in connection with post-surgical patients involve a housing with an inlet and an outlet and some form of valving arrangement so that air can be inhaled by the patient from the outlet, the path between the inlet and outlet being constricted in some fashion so that a measured amount of flow resistance is provided. This forces the patient to work against the resistance. Many such devices have indicators which can be observed by the patient as he or she inhales. One such device which is particularly beneficial is known as "the DHD coach" and is sold by DHD Medical Products Company and is identified as Model 22-4000. This particular device has a plastic housing with two major portions, one portion being a hollow cylinder with a piston movable therein. The piston is surrounded by gaskets means so that it is slidable in the cylinder and has a valve to permit a small amount of flow through the piston. The other portion has a tapered vertical channel, the bottom of which is narrower than the top. A valve member, referred to as the "coach" is freely movable in the channel and moves to the bottom, narrow end under the force of gravity. Channels within the housing are constructed so that inhalation by the patient through an attached hose draws the "coach" upwardly into the wider portion of the channel, allowing air to flow and draw the piston upwardly. In order to maintain the coach at an elevated position, the air flow rate must be increased because of the increasing width of the channel. Thus, the height of the "coach" indicates inhalation flow rate while the level of the piston indicates the total volume inhaled.
As indicated above, such devices are particularly helpful, but the problem of inducing the patient, who is frequently groggy from anesthetic and may be uncomfortable from the surgery itself, to actually use the device effectively without continual supervision is a difficult one. It is often necessary for medical personnel to visit the patient for initial instruction on how to use the spirometer, then return to be sure that it has been used, and then return again to supply nebulized medication for inhalation, commonly in the form of a decongestant or bronchial dilator. It may also be necessary to supply the patients with breathing oxygen. These various forms of attention add to the cost of postoperative care, unduly tire the patient and occupy medical personnel who are commonly needed elsewhere.